Age-related macular degeneration (AMD) is a progressive retinal disease, usually occurring at age 55 years or older, with multiple environmental and genetic factors. AMD is divided into early and late stages.
Early AMD is often called the "dry" form of the disease, while late or more severe disease progression is often referred to as "wet" AMD.
Dry AMD, the early and more common,and (typically) milder form of AMD, accounts for 85% to 90% of all cases. Early AMD is characterized by good vision and the presence of drusen and/or pigment epithelial changes with variable risk of progression to late disease. One key identifier for AMD is the collection of small, round, white-yellow, fatty deposits called drusen in the central part of the retina, the macula. Drusen accumulate in the Retina Pigment Epithelium (RPE) tissue beneath the macula and the macula thins and dries out.
The amount of vision loss is related to the location and amount of macular thinning caused by the drusen. Sometimes abnormal new blood vessels form (so called choroidal neovascularization - see below). It is therefore important for individuals with dry AMD to have their eyes examined regularly, because the dry form may eventually develop into the wet form.
Late, or wet, AMD is characterized by loss of central vision caused by geographic atrophy, neovascularization or pigment epithelial detachment. Wet AMD can rapidly damage the macula and result in a very quick loss of central vision.Although the wet form of AMD accounts for only 10 - 15% of all AMD, the risk of severe sight loss is much greater. Wet AMD is responsible for 90% of cases of severe vision loss associated with AMD. It is caused by the growth of abnormal blood vessels, or choroidal neovascularization (CNV), under the macula. These abnormal vessels leak fluid and blood into the tissue at the back of the eye, causing a blister to form in the retina. The resulting scar tissue leads first to distortion and eventually to loss of central vision. Wet AMD can rapidly damage the macula and result in a very quick loss of central vision.
Based upon the pattern of the blood vessel leakage, your doctor may classify your wet AMD as "classic" or "occult". In pure classic CNV, the blood vessels that are involved can be seen distinctly. In the pure occult form, it is impossible to locate the leaking vessels. Often patients present a combination of both occult and classic CNV with a portion showing a defined site of leakage and another portion being obscured.
The vision loss symptoms experienced with wet AMD and the availability of treatment options depend on the type of AMD but also on the location of the leakages. For wet AMD we distinguish between three different locations based on the distance between the CNV and the central part of the macula, the fovea. The three locations are: subfoveal, juxtafoveal and extrafoveal. Subfoveal, is CNV that lies directly below the fovea. Juxtafoveal and extrafoveal CNV lie progressively further away from the fovea (but still within the macula).
Another less common age-related macular disease, known as polypoidal choroidal vascularization (PCV), is more prevalent in Asia and Africa. PCV is characterized by variable degrees of severe visual loss due to polypoidal lesions and associated exudative and hemorrhagic complications.
AMD Alliance International is not a medical organisation, therefore we can only provide general information that is not intended to be a substitute for a proper medical assessment. Please read our eye health information disclaimer.